package leetcode.backtrace;

/*

编写一个程序，通过填充空格来解决数独问题。

数独的解法需 遵循如下规则：

数字 1-9 在每一行只能出现一次。
数字 1-9 在每一列只能出现一次。
数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。（请参考示例图）
数独部分空格内已填入了数字，空白格用 '.' 表示。

 

示例：


输入：board = [["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]
输出：[["5","3","4","6","7","8","9","1","2"],["6","7","2","1","9","5","3","4","8"],["1","9","8","3","4","2","5","6","7"],["8","5","9","7","6","1","4","2","3"],["4","2","6","8","5","3","7","9","1"],["7","1","3","9","2","4","8","5","6"],["9","6","1","5","3","7","2","8","4"],["2","8","7","4","1","9","6","3","5"],["3","4","5","2","8","6","1","7","9"]]
解释：输入的数独如上图所示，唯一有效的解决方案如下所示：


 

提示：

board.length == 9
board[i].length == 9
board[i][j] 是一位数字或者 '.'
题目数据 保证 输入数独仅有一个解

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/sudoku-solver
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

解法：
    1. 根据规则得到(i, j)位置可以填入的数，然后 dfs + 回溯
    2. 中间判断是否已填充完

 */

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class LeetCode37_SolveSudoku {

    boolean done;

    public void solveSudoku(char[][] board) {
        solove(board);
    }

    public void solove(char[][] board){
        if (done){
            return;
        }
        for (int i = 0; i < board.length; i++){
            for (int j = 0; j < board[0].length; j++){
                if (board[i][j] == '.'){
                    List<Character> canSetNumber = canSetNumber(i, j, board);
                    for (Character num : canSetNumber){
                        board[i][j] = num;
                        solove(board);
                        if (checkDone(board)){
                            done = true;
                            return;
                        }
                    }
                    if (checkDone(board)){
                        done = true;
                        return;
                    }else {
                        board[i][j] = '.';
                        return;
                    }
                }
            }
        }
    }

    public List<Character> canSetNumber(int i, int j, char[][] board){
        int[] arr = new int[10];
        arr[0] = 1;
        int index = -1;
        while (++index < board.length){
            if (board[index][j] != '.'){
                arr[board[index][j] - 0x30] = 1;
            }
        }

        index = -1;
        while (++index < board[0].length){
            if (board[i][index] != '.'){
                arr[board[i][index] - 0x30] = 1;
            }
        }
        int p = (i / 3) * 3, q = (j / 3) * 3;
        for (int k = p; k < p + 3; k++){
            for (int l = q; l < q + 3; l++){
                if (board[k][l] != '.'){
                    arr[board[k][l] - 0x30] = 1;
                }
            }
        }
        List<Character> result = new ArrayList<>();
        for (int k = 0; k < arr.length; k++){
            if (arr[k] == 0){
                result.add((char)(k + 0x30));
            }
        }
        return result;
    }

    public boolean checkDone(char[][] board){
        for (int i = 0; i < board.length; i++){
            for (int j = 0; j < board[0].length; j++){
                if (board[i][j] == '.') return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {

        char[][] board = {{'5','3','.','.','7','.','.','.','.'},
                {'6','.','.','1','9','5','.','.','.'},
                {'.','9','8','.','.','.','.','6','.'},
                {'8','.','.','.','6','.','.','.','3'},
                {'4','.','.','8','.','3','.','.','1'},
                {'7','.','.','.','2','.','.','.','6'},
                {'.','6','.','.','.','.','2','8','.'},
                {'.','.','.','4','1','9','.','.','5'},
                {'.','.','.','.','8','.','.','7','9'}};

        new LeetCode37_SolveSudoku().solveSudoku(board);

        System.out.println("board = " + board);

    }
}
